1. Field of the Invention
The present invention relates to apparatus and methods for repairing damaged subsea pipelines. More particularly, the present invention relates to methods and apparatus for repairing damaged sections of subsea pipeline through the use of a remotely-operated vehicle (ROV). It is still a further object of present invention to provide a method and apparatus for repairing a damaged section of a subsea pipeline in which a jumper line can be connected between the subsea pipeline in the space in which an extended length of a damaged section is removed.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
Thousand of miles of pipeline lay on the seabed. Modern pipe laying technology permits the installation of pipelines in a variety of water depths, including water depths of thousands of feet. A serious problem results when damage occurs to a pipeline set in deep water because repair can become cumbersome and difficult. Typically, submerged pipelines are damaged by an object impacting the pipeline, by an anchor dragging across the pipeline, or by the environment corroding the pipeline. If a section of pipeline becomes significantly damaged, it can require replacement.
In the past, generally two methods were employed to repair a damaged submerged pipeline. One method required the damaged section of the pipeline to be recovered to the water surface for repair on the dock of a large service vessel. After the repair was completed, the pipeline was lowered and repositioned on the seabed. A disadvantage of this method was the expense associated with recovering the pipeline to the surface. Another disadvantage with this method was that it typically could only be used with small diameter pipelines in relatively shallow water.
A second method for repairing a damage pipeline involved cutting the pipeline into two pieces near the damaged section while the pipeline remained on the seabed. The cut end of each pipe section was pulled to the surface. Once at the surface, the damaged section of pipeline was replaced with a new section. Specially designed connectors gripped the pipe at the cut ends and provided a flange or collet hub that could be used to connect the new section to the pipeline. Often, a third connector was used to make a telescopic spool section that could be expanded between the two cut ends of the pipeline to facilitate the connection. A disadvantage of this method was that the product could escape from the pipeline to the subsea environment and seawater could enter into the pipeline.
To prevent product from escaping into the environment from the cut pipeline, hot tapping systems were used to plug the pipeline. In general, hot tapping systems use a clamp-on, split tee to provide a fluid tight connection in the pipeline. A special drill was attached to the tee in a manner that prevents loss of pipeline fluid during the tapping operation. The tapping drill was fitted with a special cutter that opened a hole in the side of the pipeline. After cutting a hole in the pipeline, a stopper machine replaced the drill. The stopper machine installed an elastomeric stopper into the pipeline. After the new pipeline section was attached to the remaining pipeline, the stopper was removed but the tee became a permanent part of the pipeline.
It is known to use a remotely operated vehicle (ROV) in deep water to sever and recover a submerged pipeline. U.S. Pat. No. 5,044,827, to Gray et al., discloses a method for severing and recovering a submerged pipeline. The ROV jets beneath a portion of the pipeline and then a deflated lift bag is lowered to the submerged pipeline. The deflated lift bag is positioned under the submerged pipeline and then inflated until a section of the pipeline has been raised off the seabed. A cut-off saw is lowered to the raised section of the pipeline. The cut-off saw is clamped to the pipeline prior to severing the pipeline. The cut-off saw is then removed from the severed pipeline. A recovery head is lowered to the raised end of the severed pipeline and, after alignment, is placed in the raised end of the severed pipeline. The recovery head is activated to establish a gripping relationship with the pipeline. A recovery cable is lowered and connected to the recovery head. The recovery cable is retrieved to recover the recovery head and the pipeline to the water surface.
It becomes increasing difficult to repair a subsea pipeline when the section of damaged pipeline is extremely long. Under certain circumstances, a section of pipeline of greater than 150 feet will require replacement and repair. As such, the prior art techniques for repairing damage subsea pipelines become ineffective. Fundamentally, it is quite difficult to extend a very long section of pipeline during repair activities. It is further very difficult to connect the ends of replacement pipeline in the subsea environment. As such, a need has developed so as to be able to replace a long length of damaged section of subsea pipeline with another pipe in a convenient, effective, and easy-to-install manner.
In the past, various patents have issued relating to the repair of subsea pipelines. For example, an early patent was U.S. Pat. No. 3,508,410, issued on Apr. 28, 1970 to R. P. Lynch. This patent describes a submerged pipeline repair system in which an underwater repair chamber is adapted to straddle the submerged pipeline. Supply lines are provided for introducing a pressurized gas to displace any water therein and maintain the supply lines in a dry condition. Separate clamping mechanisms, such as pressure-actuated cylinders and piston, are located externally of the chamber and mounted at each end of a rigid support structure for engaging the pipeline on opposite sides of the chamber to prevent any movement of the pipeline.
U.S. Pat. No. 5,425,599, issued on Jun. 20, 1995 to Hall et al., also shows a method for repairing a submerged pipeline. This method includes the steps of lowering pipe support frames to the seabed and positioning the pipe support frames beneath the subsea pipeline on each side of the damaged pipeline section. The pipe support frames are expanded to elevate the damaged pipeline section. A pair of pipe attachment and receiving assemblies are lowered to the seabed and positioned astride the pipeline on each side of the damaged section of the pipeline. The pipeline is then gripped. Cutting modules are lowered and attached to the pipe attachment and receiving assemblies. The pipeline is cut at each location. A telescoping spool section is lowered to the seabed and docked into the docking modules. The telescoping spool section is expanded until the spool section engages the pipeline ends.
U.S. Pat. No. 5,458,441, issued on Oct. 17, 1995 to D. W. Barry, shows a pipe section for installation into a subsea pipeline. The pipe section provides a length of pipe having a pipe wall and at least a first bearing shoulder projecting circumferentially outward from the pipe wall so that the pipe section can be handled by supporting the pipe section from the first bearing shoulder during installation. The first bearing shoulder also prevents propagation of buckling failure in the subsea pipeline.
U.S. Pat. No. 5,518,341, issued on May 21, 1996 to Hall et al., teaches a pipe support framemov for positioning a subsea pipeline. The support frame includes upper and lower skids which are maintained in vertical alignment with one another. The lower skid includes vertical skid members and the upper skid includes matting vertical upper skid members which slidably engage the vertical lower skid members and maintain vertical alignment. Water jacking bags are positioned between the upper and lower skids to alter the elevation of the upper skid. The upper skid includes a pair of parallel beams. A trolley assembly is movably mounted to the pair of parallel beams to adjust the lateral position of the pipeline. A saddle receives the pipeline and is attached the trolley assembly. A threaded drive rod is rotatably mounted between the pair of parallel beams. The threaded drive rod is threadedly engaged with the trolley assembly such that the lateral position of the trolley assembly is controllable by manipulating the threaded drive rod.
U.S. Pat. No. 6,241,424, issued on Jun. 5, 2001 to Bath et al., provides a method and apparatus for repairing submerged pipeline. This method comprises installing a pair of hot tap tees on either side of the damaged section of pipeline, cutting a hole in the pipeline through each hot tap tee, inserting and securing plugging pigs into the pipeline, cutting and removing the damaged section of pipeline, and installing a new section of pipeline. The apparatus includes a plugging pig for use during repair of a damaged pipeline. This plugging pig has a body shaft, a cup seal secured to the body shaft for engaging an interior wall of the pipeline, a cam attached to the exterior of the body shaft, a slip assembly for sliding on the cam and engaging a slip against the pipeline wall, and a control mechanism for engaging and releasing the slip from the wall.
U.S. Patent Publication No. 2010/0047023, filed on Mar. 7, 2007, describes a pipeline repair connector for a subsea pipeline system. The connector includes a connector housing for gripping and sealing the pipeline ends, and an inlet funnel for receipt of at least one of the pipeline ends. The first part of the housing includes a pressurized gripping and sealing arrangement for receipt and gripping of an existing pipeline end in the connector housing. There is a second part of the housing that has a pressurized operated lightweight coupling for receipt and gripping of a replacement pipe in the connector housing. A pressurized alignment ball joint is intermediate between the housing and the ends. All of the components are adapted to be hydraulically pressurized in a mechanically locking position and to provide a seal to the surroundings.
It is an object of the present invention to provide a method and apparatus for repairing a damaged section of subsea pipeline that effectively establishes a fluid pathway in place of the damaged section of pipeline.
It is another object of the present invention to provide a method and apparatus for repairing a damaged section of subsea pipeline which can be carried out by an ROV in a deepwater environment.
It is still another object of the present invention to provide a method and apparatus for repairing a damaged section of subsea pipeline which can be quickly and easily installed.
It is a further object of the present invention to provide a method and apparatus for repairing a damaged section of subsea pipeline that effectively prevents leakage of pipeline fluid during the repair procedures.
It is still another object of the present invention to provide a method and system for repairing a damage subsea pipeline which allows replacement sections of greater than 150 feet to be easily installed.
These and other objects and advantages of the present invention will become apparent from a reading of the attached specification and appended claims.